1. Field of the Invention
The present invention has to do with electrically-operable strikes for locking and unlocking doors and particularly relates to apparatus and methods for horizontal adjustment of an electric strike housing within a door jamb in order to overcome preload conditions that prevent the strike from unlocking.
2. The Related Art
In most installations, when an electrically-operable strike does not release the door the problem stems from preload. Preload is a condition where the bolt of the door lock exerts pressure on the latch of the electric strike thereby preventing the mechanism from unlocking. A simple way of testing for preload is to leave the door open and check to see if the electric strike works properly by applying power to the strike (for fail-secure) or switching the power off (for fail-safe). If the strike works with the door open, the next step is to measure the position of the bolt compared with the mating surface of the latch on the strike. If the installation is too tight it may be causing a preload condition wherein the bolt applies pressure to the latch of the strike thereby pinching the locking mechanism and preventing the strike from operating properly. Preload may be caused by warping of the door, settlement of the structure around the frame, improper installation or any other conditions causing misalignment of the bolt and strike latch.
Solutions to the problem of pre-load have been disclosed in the prior art but they tend to be complex and expensive or unreliable.
U.S. Pat. No. 7,144,053 describes an electric strike assembly wherein the lip bracket can be moved relative to the housing by providing slots in the lip bracket and cooperating sawtooth elements in the housing and lip bracket. With the screws in a loosened condition the lip bracket is moved to a desired position and then the screws are tightened. The sawtooth elements then mesh together upon tightening the screws to prevent relative movement of the housing and lip bracket.
A positionable door strike is described in U.S. Pat. No. 7,240,931. A strike plate and a base plate are provided wherein the strike plate can travel relative to the base plate and the strike plate is ultimately held in its desired position with set screws.
The present invention provides an inexpensive and reliable solution to the problem created by preload conditions. And the horizontal location of the strike housing of the invention is easily adjusted using a screwdriver and pliers.
The terms “electric strike” and “strike” as used herein refer to an electrically-operable strike.